This invention relates generally to communication systems, and, more particularly, to wireless communication systems.
Wireless communication systems use a network of access nodes to provide wireless connectivity to associated geographical areas that are typically referred to as cells or sectors. The access nodes in relatively advanced systems such as systems that implement the Long Term Evolution (LTE) standards and/or protocols are referred to as evolved node Bs (eNodeBs). However, the access nodes used in wireless communication systems may also be referred to using terms including base stations, base station routers, macrocells, access points, femtocells, pico-cells, and the like. Users access the wireless communication system using access terminals that communicate with one or more of the access nodes over an air interface. The access terminals may be mobile devices such as mobile phones, smart phones, notepad computers, network computers, and the like. The access terminals may also include comparatively immobile or fixed devices such as desktop computers, wireless interface cards or radios installed in other devices, and the like.
The access nodes may be configured as elements of a self-organizing network (SON). For example, eNodeBs in a wireless communication system that operates according to LTE may be self-organizing nodes of the network. Self-organizing eNodeBs should be capable of self-configuration, self-optimization, and self-healing. Self-configuration is executed automatically after the eNodeB is deployed and includes allocating an IP address to the eNodeB, authenticating and/or downloading configuration software from an operations and maintenance (OAM) server, establishing links over interfaces between the eNodeB and other eNodeBs in the self-organizing network, and the like. Self-optimization includes optimizing the configuration of the eNodeB based upon the location of the eNodeB and measurements of the actual air interface conditions and/or channel qualities. Self-healing allows the eNodeB to mitigate some detected faults by automatically triggering appropriate recovery actions.
One example of self-healing occurs when one or more access nodes in the network detect a sleeping cell. For example, in LTE, a sleeping cell is defined as an eNodeB that is no longer functioning and yet has not triggered an alarm at a corresponding OAM server. Sleeping cell conditions can be detected on a single carrier, on a subset of carriers, or for the entire cell. The neighboring access nodes can then take predetermined actions to compensate for the potential loss of coverage resulting from the detected sleeping cell. For example, the LTE standards and/or protocols define a cell outage detection and compensation (COC) procedure that allows eNodeBs to tilt one or more antennas to provide additional wireless coverage in the geographical area served by the sleeping cell. However, the sleeping cell compensation algorithms are defined in isolation of other algorithms that are being performed by the neighboring access nodes concurrently with the sleeping cell compensation algorithm.